When making filament wound parts or workpieces, continuous fibers are conventionally wound onto a mandrel in predetermined geometric patterns using winding equipment. Creels hold the fibers and they are fed under tension. The mandrel may rotate or be passive. The orientation and thickness of the winding may be selected to match the direction and magnitude of loads in the final part or workpiece.
Typically high strength reinforcing or structural fibers such as fiberglass, e.g., E glass or S glass, and aramid, boron and carbon fibers, may be used when making filament wound parts or workpieces. The fibers are impregnated with a liquid resin, such as a polyester or an epoxy resin, via an impregnation bath or a roll applicator. The fibers are wetted before they are wound onto the mandrel. To obtain wetting, the fibers are typically drawn through an impregnation bath or passed over an applicator roll. Wetting and fill impregnation are difficult to achieve with these traditional methods. Further, these methods often result in air being trapped in the wetted reinforcement bundle. Even at slow speeds, these conventional wetting processes are only capable of wetting, impregnation and air removal of a limited number of strands. Hence, the rate of reinforcement material application which may be incorporated within filament wound parts is limited. Further, filament wound parts are made at relatively low rates due to the slow rate of wetting, making such parts expensive.
Resin baths are open or partially open to the atmosphere resulting in significant emissions into the atmosphere of environmentally unfriendly volatile organic compounds or VOC's. Further, significant resin waste commonly occurs with the use of open bath wet-out methods.
Voids are commonly found in filament wound parts which are caused by air becoming entrapped in the resin loaded onto the fibers as they pass through a resin bath or engage a roll applicator.
Hence, there is a need for an improved filament winding process and apparatus whereby: 1) higher application rates of glass reinforcement material can be wetted to reduce the time required to form a filament wound part; 2) filament wound parts can be formed with a higher reinforcement content; 3) voids in final workpieces can be reduced; 4) VOC emissions can be reduced; and 5) improved resin utilization occurs.